A four foot ramp that rises 2' is a 22 1/2⁰. Mines steeper than that it is 4' and goes up to 30" and no problems ever. I agree with the few days in the coup, I even took it further than that though. By about 3 weeks, the brooder tub in my office was getting crowded and smelly even cleaned daily, and there was noise pollution while I was on the phone doing contractor stuff. The Coup was a lot larger, but it was still cold out some days, and most nights. AND I hadn't finished the run yet. But I took them to the coup anyway with a heat lamp at three weeks. I had some 4' high 2x4 wire, and a few electric fence posts (rods), and I'd made about an 8' diameter circular pen I just moved new spots in the yard each day that it was warm enough to be out, and put them in and out by hand. I also had a furring strip and a tarp ovet half this play pen for shade. When it was cold, they didn't get out. It took longer than I expected to get their run finished, (weather and other obligations) about another 3 weeks. But they were real used to the coup by then, They had been in there the last half of their six week lives, for the most part. It took them an hour or so to decide to come down the ramp the first time, but I kept their chick feeder up in the coup for a couple more weeks, and when they saw me coming, they'd all run up the ramp and be waiting for me to open my door to the coup for food before I got there. I later added two 4x4x16" block under the bottom end of the ramp which made it not quite as steep, but I didn't do it for the steepness, I did it to get the bottom end of the wood ramp off the ground to keep it dry.
